/*
 * Copyright 2002-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.http.codec.json;

import java.io.IOException;
import java.lang.annotation.Annotation;
import java.util.List;
import java.util.Map;

import com.fasterxml.jackson.core.JsonFactory;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.JavaType;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.ObjectReader;
import com.fasterxml.jackson.databind.exc.InvalidDefinitionException;
import com.fasterxml.jackson.databind.util.TokenBuffer;

import org.reactivestreams.Publisher;

import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;

import org.springframework.core.MethodParameter;
import org.springframework.core.ResolvableType;
import org.springframework.core.codec.CodecException;
import org.springframework.core.codec.DecodingException;
import org.springframework.core.io.buffer.DataBuffer;
import org.springframework.http.codec.HttpMessageDecoder;
import org.springframework.http.server.reactive.ServerHttpRequest;
import org.springframework.http.server.reactive.ServerHttpResponse;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.MimeType;

/**
 * Abstract base class for Jackson 2.9 decoding, leveraging non-blocking parsing.
 *
 * @author Sebastien Deleuze
 * @author Rossen Stoyanchev
 * @author Arjen Poutsma
 * @see
 * <a href="https://github.com/FasterXML/jackson-core/issues/57" target="_blank">Add support for non-blocking ("async") JSON parsing</a>
 * @since 5.0
 */
public abstract class AbstractJackson2Decoder extends Jackson2CodecSupport implements HttpMessageDecoder<Object> {

    /**
     * Constructor with a Jackson {@link ObjectMapper} to use.
     */
    protected AbstractJackson2Decoder(ObjectMapper mapper, MimeType... mimeTypes) {
        super(mapper, mimeTypes);
    }


    @Override
    public boolean canDecode(ResolvableType elementType, @Nullable MimeType mimeType) {
        JavaType javaType = getObjectMapper().getTypeFactory().constructType(elementType.getType());
        // Skip String: CharSequenceDecoder + "*/*" comes after
        return (!CharSequence.class.isAssignableFrom(elementType.resolve(Object.class)) &&
                getObjectMapper().canDeserialize(javaType) && supportsMimeType(mimeType));
    }

    @Override
    public Flux<Object> decode(Publisher<DataBuffer> input, ResolvableType elementType,
            @Nullable MimeType mimeType, @Nullable Map<String, Object> hints) {

        Flux<TokenBuffer> tokens = tokenize(input, true);
        return decodeInternal(tokens, elementType, mimeType, hints);
    }

    @Override
    public Mono<Object> decodeToMono(Publisher<DataBuffer> input, ResolvableType elementType,
            @Nullable MimeType mimeType, @Nullable Map<String, Object> hints) {

        Flux<TokenBuffer> tokens = tokenize(input, false);
        return decodeInternal(tokens, elementType, mimeType, hints).singleOrEmpty();
    }

    private Flux<TokenBuffer> tokenize(Publisher<DataBuffer> input, boolean tokenizeArrayElements) {
        Flux<DataBuffer> inputFlux = Flux.from(input);
        JsonFactory factory = getObjectMapper().getFactory();
        return Jackson2Tokenizer.tokenize(inputFlux, factory, tokenizeArrayElements);
    }

    private Flux<Object> decodeInternal(Flux<TokenBuffer> tokens, ResolvableType elementType,
            @Nullable MimeType mimeType, @Nullable Map<String, Object> hints) {

        Assert.notNull(tokens, "'tokens' must not be null");
        Assert.notNull(elementType, "'elementType' must not be null");

        MethodParameter param = getParameter(elementType);
        Class<?> contextClass = (param != null ? param.getContainingClass() : null);
        JavaType javaType = getJavaType(elementType.getType(), contextClass);
        Class<?> jsonView = (hints != null ? (Class<?>) hints.get(Jackson2CodecSupport.JSON_VIEW_HINT) : null);

        ObjectReader reader = (jsonView != null ?
                               getObjectMapper().readerWithView(jsonView).forType(javaType) :
                               getObjectMapper().readerFor(javaType));

        return tokens.map(tokenBuffer -> {
            try {
                return reader.readValue(tokenBuffer.asParser(getObjectMapper()));
            } catch (InvalidDefinitionException ex) {
                throw new CodecException("Type definition error: " + ex.getType(), ex);
            } catch (JsonProcessingException ex) {
                throw new DecodingException("JSON decoding error: " + ex.getOriginalMessage(), ex);
            } catch (IOException ex) {
                throw new DecodingException("I/O error while parsing input stream", ex);
            }
        });
    }


    // HttpMessageDecoder...

    @Override
    public Map<String, Object> getDecodeHints(ResolvableType actualType, ResolvableType elementType,
            ServerHttpRequest request, ServerHttpResponse response) {

        return getHints(actualType);
    }

    @Override
    public List<MimeType> getDecodableMimeTypes() {
        return getMimeTypes();
    }

    // Jackson2CodecSupport ...

    @Override
    protected <A extends Annotation> A getAnnotation(MethodParameter parameter, Class<A> annotType) {
        return parameter.getParameterAnnotation(annotType);
    }

}
